Portable gas-powered tool with linear motor

ABSTRACT

An efficient, portable, easy to operate tool employing a linear motor is disclosed that is powered by the gases produced from the internal combustion of a fuel and air mixture. A supply of liquified gas stored under pressure in a cylinder provides the source of power. The linear motor is slidably mounted within a cylinder to move reciprocally downwardly and upwardly through a driving and return stroke. A combustion chamber is formed at the upper end of the cylinder. A spark plug powered by a piezo-electric firing device is located within the combustion chamber. The combustion chamber features a turbulence generator, such as a fan, driven by an electric motor which is continuously in operation when the tool is in use. A main valve mechanism actuated by a set of lifting rods that are moved upwardly and downwardly when the tool is moved towards and away from the workpiece, is used to control the opening and closing of the combustion chamber and to control the flow of fresh air through the combustion chamber. When the combustion chamber is isolated from the atmosphere and the fuel and air are thoroughly mixed, the spark plug is fired to explode the fuel and air mixture and force the linear motor through its driving stroke. The linear motor is returned to its driving position by a spring or air acting against the underside of the linear motor. The unique use of the electric fan improves the overall operational efficiency of the tool and the utilization of the liquified combustible gas.

This application is a continuation, of application Ser. No. 227,193,filed Jan. 22, 1981 now abandoned.

TECHNICAL FIELD

This invention relates generally to a portable tool which employs alinear motor that is self-contained and is operated by the products ofcombustion. It requires no separate starting mechanism. Connected to andoperated thereby can be various types of attachments, such as, shearingand cutting devices, marking members, hole piercing devices, etc. Inaddition, the motor can be used to drive members disposed therebeneathfrom a magazine; such as hog rings, animal tags and fasteners of alltypes, including nails, rivets, etc.

Portable-type tools, of course, have been available for long periods oftime, and a typical tool is one such as a fastener driving tool fordriving nails, or other types of attachments by means of air pressure,battery power, or using some sort of explosive device. Where it isdesired to have substantially large forces applied, the compressed airor explosive devices have been used. These types of devices have obviousdrawbacks. In the case of compressed air, there is required a compressorwhich becomes a burden and an inconvenience in addition to the largeinitial expense required for investment in such equipment. Whenexplosive devices are used, the operating cost of such unit is high andthey cannot be operated for any substantial period of time withouthaving to be refilled. Thus, it can be appreciated that where it isdesired to have a truly portable tool which is capable of generatinglarge forces without requiring an auxiliary power source, such a toolwould have many uses.

SUMMARY OF THE INVENTION

The present invention relates to a portable tool powered by the gasesproduced from the combustion of a fuel and air mixture within a confinedspace. The available power acts on a linear motor which through theaction of a mechanism connected to the motor can be used to drivefasteners, operate shearing devices, and other attachments that requirerelatively large forces.

There are illustrated in the attached drawings three embodiments oftools employing a linear motor in which the force output of the linearmotor is generated independent of the movement of the motor itself.Specifically, a sealed combustion chamber is provided with a turbulentmixture of fuel and air that is ignited to drive the motor to effectuatethe desired action of the tool. No starter or other device is employed.

In one embodiment, there is illustrated a portable tool having a linearmotor consisting of a piston having a rod connected thereto. The pistonforms one wall of the combustion chamber. The motor is driven in thedownward direction and the motor is returned by a spring back to itsposition to await another firing. In a second and third embodiments,there is illustrated the utilization of the linear motor for drivingfasteners into a workpiece. These are, of course, but two specificapplications of the present invention and are not intended to belimiting, since obviously the inventive concepts disclosed therein canbe used for other purposes in other types of portable tools.

Essentially, the three tools illustrated have in common an arrangementincluding a main cylinder within a housing that guides a piston duringits reciprocation between the driving and return strokes. The pistoncarries a driving member, which in one case can be connected to asuitable attachment for shearing, cutting, punching, etc., and in theother two embodiments is used to drive a fastener into a workpiece.

A combustion chamber is formed in the housing adjacent the upper end ofthe main cylinder by the inside of the housing, the piston, and a mainvalve mechanism which controls the flow of air between the atmosphereand the combustion chamber. In the combustion chamber is located a fanthat is started when the tool is gripped, or when a switch associatedwith the fan is actuated, to provide turbulence in the combustionchamber which increases the efficiency of the tool. In one of theembodiments, the main valve mechanism is controlled by actuation of thetrigger, and in the other two embodiments, while the trigger isinvolved, it is necessary to engage a bottom trip mechanism. The bottomtrip mechanisms employed are to insure that in at least those twoembodiments the tool cannot be fired unless it is engaged with theworkpiece. This is a safety feature for fastener driving tools and neednot necessarily be employed, depending on the type of tool and the useto which it is being put.

It is to be noted that the two embodiments illustrated for drivingfasteners are described in detail in an application filed simultaneouslyherewith in the name of the same inventor and assigned to the assigneeof the present invention. These embodiments will be described in generaldetail in this application, and any further specific information desiredcan be obtained by referring to the aforesaid application and isincorporated by reference herein, if needed, to have a more detailedunderstanding of the specifics of the two fastened driving tools.

Referring again to the operation of the tools, it is noted thatactuation of the trigger results in a metered amount of fuel beingintroduced into the combustion chamber after the chamber has been sealedand subsequent actuation of a spark plug to ignite the turbulent mixtureof gas and air in the dombustion chamber to drive the linear motor,which in this case is a piston. In one instance, the piston is returnedto its driving position by a spring, and in the other embodiments, thepiston is returned to its driving position by differential air pressure.When the pistons have been returned to their driving positions, they areretained in place by the spring in the first embodiment and by frictionin the other two embodiments.

Filed concurrently with this application on Jan. 22, 1981, was anapplication Ser. No. 227,194, now U.S. Pat. No. 4,403,722 entitled"Combustion Gas-Powered Fastener Driving Tool," in the name of the sameinventor and assigned to the same assignee. This application is directedto fastener driving tools employing a motor of the general type setforth herein.

Numerous other advantages and features of the invention will becomereadily apparent from the following detailed description of thedescribed embodiments, from the claims, and from the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional side elevational view of a portabletool embodying the subject invention and illustrating the relativeposition of the principal components prior to the tool being operated;

FIG. 2 is a partial cross-sectional side elevational view of a secondembodiment of the present invention, a fastener driving tool, andillustrating the position of the principal components before the toolhas been fired;

FIG. 3 is a partial cross-sectional side elevational view of thefastener driving tool as shown in FIG. 2 illustrating the position ofthe major components located at the lower end of the barrel section atthe end of the linear motor driving stroke;

FIG. 4 is an enlarged partial cross-sectional side elevational view ofthe components forming the ignition mechanism of the embodiment of FIG.2;

FIG. 5 is a schematic diagram illustrating the ignition circuit of theembodiment of FIG. 2;

FIG. 6 is a view similar to FIG. 1, but illustrating a third embodimentof a tool embodying the present invention;

FIG. 7 is a partial cross-sectional side elevational view illustratingdetails of the safety trip mechanism used in the tool shown in FIG. 6;

FIG. 8 is a partial cross-sectional plan view of the fastener drivingtool of FIG. 7 taken along line 8--8;

FIG. 9 is an enlarged cross-sectional view of the cap operation of thefuel injection mechanism of the tool illustrated in FIG. 7;

FIG. 10 is an enlarged cross-sectional view of the fuel metering valveof the present invention;

FIG. 11 is an enlarged cross-sectional view of a source of fuel usedwith the present invention; and

FIG. 12 is a cross-sectional view taken along line 12--12 of FIG. 11.

DETAILED DESCRIPTION

This invention is susceptible of being used in many different types oftools. There is shown in the drawings and will herein be described indetail three embodiments of the tools incorporating the invention, withthe understanding that these embodiments are to be considered butexemplifications, and that it is not intended to limit the invention tothe specific embodiments illustrated. The scope of the invention will bepointed out in the claims.

EXTERIOR FEATURES

FIG. 1 illustrates a tool 20 including a housing 22 forming a handleportion of the tool and a cylinder 24 in which the linear motor, hereina piston 26, is disposed. Connected to the piston 26 is an operator orworking member 27, which is connected to the desired attachment to beoperated by the linear motor, or which can engage various devices forintroduction into the workpiece, or for any other disposition. Thelinear motor or piston 26 is retained in the position shown by a spring28. The housing 22 includes stop members 29 which extend radiallyinwardly to limit the upward travel of the piston 26.

Located within the housing 22 between a cap 32, the piston 26 and theadjacent sidewalls of the housing 22 is a combustion chamber 30. The capis maintained in position relative to the housing by bolts 34.

Located within the combustion chamber 30 is a fan blade 36 which isconnected to a shaft 38 operated by the electric motor 40. Actuation ofthe motor results in the fan creating a turbulence in the combustionchamber, which aids in increasing the efficiency of the tool byproviding an improved air-fuel mixture, and improved ignition and flamepropagation. The electric motor 40 is operated by a battery 42 locatedin the handle portion of the tool and interconnected by suitableconnections, not shown. Also disposed in the combustion chamber is thespark plug 44, which is ignited by a suitable circuit describedhereinafter.

It is to be noted that provision is made for a space 48 to be providedbetween the cap 32 and the housing 22 to permit the exhausting of gasesfrom the combustion chamber 30 when the sleeve 50 surrounding thehousing 22 is in the position shown in FIG. 1 as is shown by thedirectional arrows. Cylinder 24 includes a slightly enlarged diameterupper end 24a, so that air can flow around the piston 26 and associatedO-ring when the piston is in the raised or driving position of FIG. 1,and stop members 29 are circumferentially spaced from one another todefine gaps 29a through which air may flow into the combustion chamber.A plurality of air inlet openings 24b are provided adjacent the lowerend of cylinder 24 for introducing air into the cylinder.

Extending downwardly from the sleeve 50 is a depending portion 51 whichis interconnected to the trigger mechanism 54 in the following manner.The trigger mechanism 54 includes a trigger 55 which is connected to alink 56, the left-hand end of which is connected to the dependingportion 51 through a pin 58 extending through a slot 60 in the link 56.Thus, it can be seen that upward movement of the trigger 55 will resultin upward movement of the sleeve 50 to close off the combustion chamberfrom atmospheric air.

The operation of the trigger 55 also operates the fuel control mechanism52. The fuel control mechanism includes a rod 68 that extends downwardlyinto engagement with the trigger 55. This position is maintained asshown in FIG. 1 by a compression spring 62 which extends between thefuel control valve housing 64 and a flange 66 integral with the rod 68.

The details of the fuel control mechanism include the housing 64 and thevalve stem 70 which is provided with lands 72, 74. The space between thestem 70, housing 64, and lands 72, 74 defines a metering chamber 76. Inthe position shown in FIG. 1, fuel is provided in the metering chamber76 from the fuel container assembly 80 by the action of a fuel controlvalve 75. When the trigger 55 is moved upwardly the land 74 blocks offthe entrance from the fuel container 80 and the land 72 unblocks theport 79 to interconnect the metering chamber 76 with the combustionchamber 30. Thus, the metered amount of fuel is introduced into thecombustion chamber upon upward movement of the trigger 55. The design issuch that the metering chamber 76 is opened to the combustion chamber 30after the sleeve 50 has closed off the combustion chamber from theatmosphere.

A switch 77 is mounted on the housing of the tool, and is connected bysuitable means, not shown, to the fan motor 40 so that the fan isoperated when the switch 77 is actuated. It should be noted that theoperator shall engage the fan switch 77 which turns the fan on toprovide turbulence in the chamber 30 prior to operating the tool bymovement of trigger 55. In addition, it is seen that the fuel containerassembly 80 includes a pressurized chamber 82 which acts against thepiston 84 to maintain the fuel in the container 80 in liquid form. Thetrigger further acts to force together crystals located in apiezoelectric device schematically illustrated at 46. Effectively upwardmovement of the link 56 about pivot pin 57 acts to force together twocrystals disposed in device 46 to generate a voltate to power the sparkplug 44. Further details of the device will be described in conjunctionwith FIGS. 4 and 5 herein, which specifically illustrate a piezoelectricdevice and the firing circuit.

Briefly, this tool operates as follows. First, the fan is started byengaging the switch 77. Upward movement of the trigger 55 closes off thecombustion chamber 30 by moving the sleeve 50 to close off the exhaustport 48. As this occurs, further upward movement of the rod 68introduces the fuel from the metering chamber 76 into the combustionchamber 30. The upward movement of the trigger 55 energizes thepiezo-electric system 46, which provides a spark to the plug 44, whichignites the fuel to drive the linear motor piston 26 downward againstthe action of the spring 28. As soon as the piston 26 begins to movethrough its driving stroke, the O-ring thereon seals against thesidewall of cylinder 24 and air below the piston is expelled throughopenings 24b. When the piston 26 reaches the driven position at the endof its driving stroke, it engages a resilient bumper 86 at the lower endof cylinder 24.

When the trigger is released, the sleeve 50 moves downwardly and thechamber 30 is opened to atmosphere through ports 48. The fan blades havea slight pitch to scavenge the rest of the gases and introduce the freshair into the combustion chamber for the next firing, as is clear fromthe directional arrows. The piston 26 is returned to the position shownin FIG. 1 by the spring 28, and a second metered quantity of fuel isprovided to the chamber 76, so that the tool is in position to be fireda second time.

Reference is now made to FIGS. 2-5, which illustrate a portable fastenerdriving tool employing the novel linear motor.

Referring first to FIG. 2, there is illustrated a fastener driving tool100, the principal components of which are attached to or carried by agenerally hollow housing 102. The housing 102 of the tool 100 has threemajor sections: a barrel section 108, a graspable, elongated handlesection 110 extending horizontally outwardly from a position generallymidway of the barrel section, and a base 106 extending under the barrelsection and the handle section. Located within the barrel section 108 isa main cylinder 104 in which the linear motor is located. Included inthe base 106 is a magazine assembly 112 holding a row of nails disposedtransversely to the path of a fastener driver 132 that is connected toand operated by the linear motor, which in this case is a working pistonassembly 130.

The lower end of the barrel section 108 carries a guide assembly 152which guides the fastener driver toward the workpiece. The magazine 112supplies fasteners serially under the fastener driver 132 into the guideassembly 152 to be driven into the workpiece. The base 106 also supportsa holder 116 containing a plurality of dry cells which form the powersource 118.

A fuel tank 114 is mounted between the barrel section 108 and the handleportion 110 of the housing 102. The fuel tank 114 is filled with aliquefied, combustible gas kept under pressure, such as, MAPP gas orpropane, which vaporizes when it is discharged into the atmosphere. Thefuel tank 114 is supported by a pivoted lower bracket 200 and a fixed,generally U-shaped upper bracket 202. The upper end of the fuel tank 114carries a valve assembly 204 for metering fuel out of the tank. Aflexible plastic cover 210 pivotably joined to a cover member 168 fitsinto the upper bracket 202 to retain the fuel tank in place. The cover210 is opened when the fuel tank 114 must be replaced. The cover 210provides a downward force which snugly holds the lower end of the fueltank within the lower bracket 200. At this point, it should be notedthat the upper bracket 202 has an inside dimension greater than theoutside dimension of the fuel tank 114.

In particular, this dimension is selected so that when the upper end ofthe fuel tank is forced towards the upper end of the barrel section 108of the housing 102, the valve assembly 204 will be actuated to dispensea metered quantity of fuel. The manner in which this is accomplishedwill be explained after the interior components of the tool have beendescribed.

BARREL SECTION

At the interior of the lower end of the barrel section 108 of thehousing 102, there is located the open-ended cylinder 104. The cylinderwill hereinafter referred to as the "main cylinder." The diameter of themain cylinder 104 relative to the diameter of the barrel section 108 ofthe housing 102 is such that an open generally annular zone or region134 is formed. The barrel section of the housing 102 is formed withperihperal openings 103, which allows air to pass freely around theexterior of the main cylinder 104.

The driving piston 130 is mounted within the main cylinder and carriesthe upper end of the fastener driver 132. The upper end of the barrelsection 108 of the housing 102 carries an electrically powered fan 122and a main valve mechanism 124, which controls the flow of air betweenthe combustion chamber 120 and atmosphere. The upper end of the housinglocated above the fan is closed by the cylinder head 126. The main valvemechanism 124 includes an upper cylinder 136, which together with thecylinder head 126, the main cylinder 104, and the piston 130 forms thecombustion chamber 120. The electric fan includes a set of blades 123which are joined to the output shaft of the electric motor 122.

The main cylinder 104 is closed at its lower end by a cup-shaped supportcasting 128 that is suitably supported in the barrel section. Locatednear the bottom of the cylinder 104 are a series of exhaust ports 156that are closed off by exhaust valves 172 that are located to controlthe flow of gas out of the cylinder 104 when the piston linear motor 130passes the ports 156. Connected to the cylinder 104 adjacent the ports156 is an annular ring-shaped casting 173. At the bottom of the cylinder104, a seal 158 is used to plug the center of the support casting 128.Also located in the support casting 128 are a plurality of ports 176which interconnect the bottom of the cylinder 104 with the chamber 146in which there is located a spring 148 for reasons to be describedhereinafter.

The piston 130 moves between the opposite ends of the main cylinder 104.The upward and downward movement of the piston defines the driving andreturn strokes of the piston. As previously mentioned, valves 172 permitexhausting of the gas above the piston when the piston passes the ports156 and the valves 174, which remain closed during the downward movementof the piston, provide for a compression of the air beneath the pistonto provide a bumper preventing the piston from engaging the bottom ofthe cylinder. These valves 174 also function to open and introduce airinto the space between the piston after the piston begins to be returnedto its driving position. The piston 130 carries the fastener driver,which extends through the seal 158 and into the guide assembly 152. Theguide assembly is configured to pass individual fasteners 154 that aredisposed therein by the magazine 112, so that when the piston 130 isdriven through its driving stroke a fastener is driven into a workpiece.

It is to be noted that the piston 130 includes a pair of O-rings thatare sized so that the frictional force between the piston and the insidesidewalls of the main cylinder is sufficiently great so that in theabsence of the differential pressure across the piston it will remain inplace relative to the interior sidewalls of the main cylinder when it isreturned to its driving position. The upward movement of the piston 130is limited by an overhang of the cylinder 104.

The cylinder 136 constituting the valve control for the combustionchamber is free to move between the lower position shown in solid linesin FIG. 2 wherein the combustion chamber is open to atmosphere to permitair to flow in, as shown by the arrows 226 and an upper position shownin dotted lines wherein the combustion chamber is sealed off from theatmosphere by the O-ring 162 provided in the cap 126 and the O-ring 160provided in the main cylinder 104. Air is thus free to enter through theupper opening 140 when the tool is in the position shown in FIG. 2 andexpended combustion gas is free to exit from the combustion chamber 120through the opening 138. The downward movement of the cylinder 136 islimited by engagement of inwardly extending fingers 170 on cylinder 136with cylinder 104.

It is essential to provide turbulence in the combustion chamber 120 tomaximize the operating efficiency of the tool.

When the chamber 120 is opened to atmosphere, the position andconfiguration of the rotating fan blades 123 causes a differentialpressure across the combustion chamber 120. This action creates movementof air in the chamber 120 and forces air in (arrow 226) through theupper openings 140 and out (arrow 224) through the lower openings 138.When the combustion chamber is sealed off from the atmosphere, andturbulence is created in the combustion chamber by rotation of fan 123,fuel is injected and the mixture is ignited. The flame propogationenhanced by the turbulence substantially increases the operatingefficiency of the tool.

To insure that the tool cannot be fired until it is in engagement withthe workpiece, the movement of the cylinder 136 is effected by a bottomtrip mechanism which is operated when the tool is brought into contactwith a workpiece into which a fastener is to be driven. In theembodiment illustrated in FIG. 2, it includes a spring-loaded casting towhich are connected lifting rods that are used to raise and lower thecylinder 136. Specifically, a Y-shaped casting 142 is located in thechamber 146 between the guide assembly 152 and the lower end of thesupport casting 128. Connected to the casting are three lifting rods144A, B and C which interconnect the casting 142 to the cylinder 136.Extending downwardly from the casting 142 is a cylinder mount 147. Thespring 148 in the chamber 146 acts to bias the casting 142 into theposition shown in FIG. 2. Located within the cylindrical mount 147 isthe main lifting rod 150 which when moved upwardly moves the rods 144A,B, and C upwardly, which carries with it the cylinder 136 to close offthe combustion chamber. The design is selected so that engagement of themain lift rod with the workpiece raises the cylinder 136 the prescribedamount to the broken line position shown in FIG. 2 to seal thecombustion chamber. Accordingly, when the tool is lifted off from theworkpiece, the spring 148 biases the lifting rod 150 downwardly to movethe cylinder 136 to the full line position shown in FIG. 2 wherein thecombustion chamber is open to atmosphere.

All the major components fitting within the barrel section 108 of thehousing 102 have been described with the exception of those componentsthat are joined to the cylinder head 126.

The cylinder head 126 carries the electric fan 122, a spark plug 164,and provides an internal passageway 166 through which fuel is injectedinto the combustion chamber 120.

The components located within the handle section 110 of the housing 102will now be described.

HANDLE SECTION

The handle section 110 contains the controls used to operate the tool100. In particular, the handle section 110 contains a "deadman's" switch178, a trigger mechanism 180, a piezoelectric firing circuit 182, whichactivates the spark plug 164, a portion of a fuel ejecting mechanism184, which introduces fuel into the combustion chamber 120 via thepassageway 166 in the cylinder head 126, and a firing circuit interlockmechanism 188, which locks and unlocks the trigger mechanism 180.

The deadman's switch 178 is mounted at the top of the handle 110. It issuitably connected through appropriate mechanism to operate the electricmotor 122 to drive the fan 123. Thus, it can be seen that when the userof the tool grips the handle in the forward position, the fan 122 isactuated to provide turbulence in the combustion chamber 120.

The trigger mechanism 180 mounted in the handle includes a lever 190which is pivotally connected to a piezoelectric firing circuit 182 by apin 192. The trigger button 194 is joined by a pivot pin 196 to the fuelejecting mechanism 184.

The fuel ejecting mechanism 184 which functions to introduce aprescribed metered amount of fuel into the combustion chamber, includesan actuating link 212 which interconnects the trigger 194 to a cammingmechanism 214. The operation of the trigger through the linkage 212 andcamming mechanism 214 acts to move the fuel tank 114 to the left, whichresults in depression of the outlet nozzle 206 to introduce a meteredamount of fuel into the passageway 166 from the metered valve assembly204. It is noted that the tank 114 is retained in position by means ofthe cover 210 which is interengaged with the upper bracket 202. When thetrigger is released, the spring 208 acts to return the fuel tank to theposition in FIG. 2.

The fuel injected into the combustion chamber 120 is ignited by a sparkplug 164 powered from the piezo-electric firing circuit 182. FIGS. 4 and5 illustrate the firing circuit 182. According to the piezoelectriceffect, voltage is produced between opposite sides of certain types ofcrystals 182A, 182B when they are struck or compressed. Here a cammingmechanism actuated by the lever 190 and pivot pin 192 is used to forcetogether the two crystals 182A, 182B. An adjusting screw 183 sets thepreload to the assembly. A schematic diagram of the electrical circuitbetween the spark plug 164 and the piezo-electric firing circuit 182 isillustrated in FIG. 5 and includes a capacitor C and a rectifier R. Thecapacitor C stores energy until the spark discharges, and the rectifierR permits spark to occur when the trigger is squeezed and not when thetrigger is released. The piezo-electric firing circuit 182 is trippedwhen the lever 190 is raised upwardly by the trigger mechanism 180.Before the firing circuit can be refired or recycled, the lever 190 mustbe lowered to cock the cam used to force the two crystals 182A and 182Btogether.

There remains to describe the firing circuit interlock mechanism whichprecludes firing of the tool until all components are in their properposition. This includes links 216 which are connected to the triggermechanism 180 by a tension spring 220 and a pivot pin 222. Connectinglinks 216 are located on opposite sides of the fuel tank 114. It can beappreciated that with the pin 218B located in the slotted opening 198 ofthe handle 110 that until the cylinder 136 is moved upwardly by theupward movement of the rods 144A, B, and C, the trigger cannot beactuated to form the spark to ignite the fuel in the combustion chamber.Upward movement of the rods 144A, B, and C moves the links 216 upwardlyand withdraws the pin 218B out of the slot 198, thus permitting thetrigger 194 to be moved upwardly to introduce the metered fuel into thecombustion chamber and actuate the piezoelectric circuit. Stated anotherway, the trigger cannot be actuated to introduce fuel and create a sparkuntil the workpiece is engaged to move the guide assembly upwardly,which moves the casting 142 upwardly to free the trigger 194.

Briefly, the tool disclosed in FIGS. 2-5 operates as follows.

Grasping of the tool 110 engages the deadman's switch 178 to start thefan motor 122 to rotate the blades 123 to provide turbulence in thecombustion chamber 120. With the electric fan running, a differentialpressure is produced across the combustion chamber, which acts to forcefresh air in (arrow 226) through the upper openings 140 and out (arrow224) through the lower opening 138. The rotating fan blades produce aswirling turbulent effect within the combusiton chamber. Any combustiongases remaining in the combustion chamber due to the previous operationof the tool are thoroughly scavenged and discharged from the combustionchamber by operation of the electric fan 122.

When the tool is positioned on the workpiece, the main lifting rod isdepressed, as shown in FIG. 3, which overcomes the force of the biasingspring 148 to move lifting rods 144A, B, anc C, and the cylinder 136from its lower position shown in solid lines to its upper position shownin dotted lines to seal off the combustion chamber 120. This upwardmovement of the lifting rods also activates the firing circuit interlockmechanism 188. That is to say that the links 216 and associated pins218B are pulled out of the slot 198, thus permitting the trigger 194 tobe moved upwardly. Upward movement of the trigger 194 actuates the fuelinjecting mechanism by moving the container to the left through theaction of the linkage 212 and camming mechanism 214. This results inengaging the metering valve assembly 204 to introduce a metered amountof fuel into the passageway 166 and the combustion chamber 120. Duringupward movement of the trigger 194, the crystals 182A and 182B areforced together to actuate the piezo-electric firing circuit 182, whichfires the spark plug 164 in the combustion chamber 120.

The rapid expansion of the exploding air and fuel mixture pressurizesthe upper face 130A of the piston 130 and drives the fastener driverdownwardly wherein it forces a fastener 154 into a workpiece. Inaddition, the movement of the piston 130 through its driving strokecompresses the air within the main cylinder 104 bounded by the lowerface of 130B of the piston and the inside of support casting 128. As thepressure increases below the piston 130, the exhaust valve means 172 onthe sidewalls of the main cylinder 104 pops open. As long as the exhaustvalve means 172 is open, the pressure cannot build up on the lower face130B of the piston 130. When the piston 130 passes below the ports 156,the air bounded by the lower face of the piston and the inside of thesupport casting is now isolated from the atmosphere, and the pressure onthe lower face 130B of the piston rapidly increases. Effectively, acompression chamber has been formed in the lower end of the maincylinder which functions as a bumper to prevent the piston from strikingthe support casting 128.

Once the piston 130 has passed the ports 156 on the sidewalls of themain cylinder 104, the combustion gases are free to flow out of the maincylinder 104 through the exhaust valve means 172 to the atmosphere. Thetemperature of the gases in the combustion chamber rapidly drops fromapproximately 2000° F. to 70° F. in about 70 milliseconds due to theexpansion of the gases as the piston moves downwardly and the coolingeffect of the walls surrounding the expanding gases, and this suddentemperature drop produces a vacuum within the combustion chamber 120.Once the pressure within the combustion chamber is below atmosphere, theexhaust valve means 172 shuts off.

As soon as the pressure on the upper face 130A of the piston 130 is lessthan the pressure on the lower face 130B, the piston will be forcedupwardly through its return stroke. Initially, this upward movement iscaused by the expansion of the compressed air within the compressionchamber (see FIG. 3). Subsequent movement is caused by the pressure ofthe atmosphere, since the thermal vacuum formed within the combustionchamber 120 is on the order of a few psia. Additional air is supplied tothe lower face 130B of the piston 130 through the return valves 174which are operated by the atmospheric pressure. The piston 130 willcontinue upwardly until it engages the lip on the cylinder and willremain suspended at the upper end of the main cylinder by virtue of thefrictional engagement between the sealing rings and the cylinder wallplus the force of the seal 158 on the fastener driver 132.

If the tool 100 is then lifted clear of the workpiece the main liftingrod 150 is forced outwardly by its main biasing spring 148. Since theelectric fan 123 is still in operation, any remaining combustion gasesare forced out of the lower openings 138, and fresh air is drawn inthrough the upper openings 140. This prepares the tool for firinganother fastener into the workpiece. When the trigger button 194 isreleased the piezo-electric system 182 is reset or cocked for asubsequent firing period. When the main lifting rod 150 is drivendownwardly by the biasing spring 148, the lock pin 218B within thefiring circuit interlock mechanism 188 is forced back into the slottedopening 198 in the housing. This prevents subsequent operation of thetrigger mechanism until the tool 100 is properly positioned on theworkpiece and the combustion chamber is isolated from the atmosphere.

Referring now to FIGS. 6-9, there is illustrated another embodiment of aportable fastener driving tool employing the novel linear motordescribed hereabove.

The fastener driving tool illustrated in FIGS. 6-9 is similar in manyrespects to that illustrated in FIGS. 2-5. The portions of the tool inFIG. 6 that are substantially identical with those illustrated in FIG. 1have been given the same numerals and will only be briefly referred toherein. However, the aspects of the tool in FIGS. 6-9 that differ fromthose illustrated in FIGS. 2-5 will be dealt with in detail.

The principal components of the second embodiment of the fastenerdriving tool 101 disclosed in FIG. 6 are very similar to those in FIG. 1in that the tool in FIG. 6 contains housing 102 including a barrelsection 108, a graspable elongated handle section 110 extendingoutwardly from a position generally midway of the barrel section, and abase 106 extending under the barrel section and the handle section.Included in the base 106 is a magazine assembly 112 holding a row ofnails disposed transversely to the path of the fastener driver 132.Essentially, the barrel section of the tool including the fan 122,piston assembly 130, main valve means 124, and a bottom trip safetymechanism are very similar to that disclosed in FIGS. 2-5, except forthose differences to be discussed hereinafter. Specifically, themechanism for positioning the upper cylinder 136 that constitutes a mainvalve means to control the opening and closing of the combustion chamber120 is slightly different from that disclosed in FIG. 2. Briefly, upwardmovement of the lifting rod 150 by bringing the tool into contact withthe workpiece acts to move the rod support 143 upwardly against theaction of the spring 148. As shown in FIGS. 7 and 8, the rod support 143is essentially X-shaped and connected to each of these leg portions arelifting rods 145A, 145B, 145C, and 145D, which, as shown in FIG. 7, havetheir upper ends disposed in the annular slot 137 of cylinder 136.Engagement of lifting rod 150 with the workpiece will raise the rodsupport 143 and rods 145A-D to move cylinder 136 upwardly and bring theupper portion of cylinder 136 into sealing contact with O-ring 162 andthe lower portion of cylinder 136 into sealing contact with O-ring 160to seal off the combustion chamber.

Another difference between the two embodiments is that in the embodimentshown in FIG. 6, upward movement of the cylinder 136 acts to introduce ametered amount of fuel into the combustion chamber. This action takesplace through the action of the cylinder 136 engaging depending arm 232of the cap 228. Upward movement of the cap 228 acts to pivot the cap 228about the pivot pin 230, with the result that valve assembly 204 ismoved inwardly to admit a metered amount of fuel into the passageway 166leading into the combustion chamber 120. Counterclockwise movement ofthe fuel tank 114 is permitted by the resilient pad 117 upon which thetank 114 rests within its support.

Other differences from the tool of FIG. 1 located in the barrel portionof the tool include a spring 151 within the cylindrical mount 147, whichspring is disposed between the rod support 143 and the lifting rod 150to insure that the lifting rod will always be moved to its outwardposition when the tool is moved away from the workpiece, irrespective ofwhether or not the cylinder 136 has been moved to its downward positionby the action of the spring 148.

Another difference between the two embodiments is the bottom safetymechanism disclosed in FIG. 6, which prevents movement of the trigger tobring about firing of the tool until the tool engages a workpiece. Thetool of FIG. 6 employs a safety latch mechanism 242, which when the toolis out of engagement with the workpiece is positioned so that the latcharm 244 thereof prevents trigger actuating movement of the trigger 194by virtue of engagement between the latch arm 244 and the flange 240that extends outwardly from the trigger leg 238 of the trigger 194. Thetrigger latch 242 is maintained in the position shown by the action of atorsion spring 248 which is located about the pin 248a whereby thesafety latch is connected to the tool housing 110. It is seen that thelatch 242 is moved out of engagement with the trigger 194 by the upwardmovement of the lifting rod 150. The lifting rod 150 is connected to thering 250 through the cylindrical mount 147. The ring 250 has an arm 252that is normally in engagement with the latch arm 246. Thus, when thelift rod 150 moves upwardly, the ring arm 252 pivots the safety latch242 in a clockwise direction to move the latch arm 244 out of engagementwith flange 240. The trigger 194 is now free to move and its upwardmovement moves the lever 236, which actuates the piezoelectric circuitto send a charge to spark plug 164 and ignite the fuel and air mixturecontained in the combustion chamber.

OPERATION OF TOOL ILLUSTRATED IN FIGS. 6-9

Grasping of the handle 110 in the forward position by the user will tripthe deadman's switch 178 and start the electric fan 122. When the toolis put into contact with a workpiece, the main lifting rod 150 is movedupwardly against the spring 148 to raise cylinder 136 and seal off thecombustion chamber 120. As in the case with the tool illustrated in FIG.2, the actuation of the electric fan before the upward movement of thecylinder 136 results in there being swirling, turbulent air in thecombustion chamber.

The upward movement of the cylinder 136, in addition to sealing off thecombustion chamber, results in introduction of a metered amount of fuelinto the combustion chamber through passageway 166. This occurs as aresult of the cylinder 136 engaging the depending arm 232 of the cap228, which acts to swing the cap 228 upwardly and move the tank 114 in acounterclockwise direction to actuate the fuel valve assembly todispense a metered amount of fuel into the chamber 120.

The upward movement of the lifting rod 150 moves the safety latch 242 ina clockwise direction to disengage the latch from the trigger mechanismto permit the trigger 194 to move upwardly. Upward movement of thetrigger 194 results in actuating the piezo-electric firing circuit whichfires the spark plug 164 in the combustion chamber 120. The piston 120is then driven downwardly to drive a nail into a workpiece. The returnaction of the piston and the scavenging of the combustion chamber isidentical with that which occurs in the tool of FIG. 2, and furtherrepetition of that operation is not believed necessary.

FUEL SUPPLY FOR EMBODIMENTS OF FIGS. 2-5 AND FIGS. 6-9

A preferred form of metering valve is shown generally at 300 in FIG. 10.Valve 300 includes a valve body 301 having a fuel inlet stem 302, and afuel outlet stem 303 having passages 304 and 305, respectively. Valvebody 301 includes a bushing 306 seated within a generally cylindricalcavity 307, and bushing 306 is provided with a cylindrical cavity 308which defines a metering chamber.

A coil spring 310 is mounted in a cylindrical cavity 311 in valve body301 and bears against a spring seat 312 carried at the reduced diameterend 313 of stem 303. An O-ring 314 is disposed around stem portion 313,and is loosely received between a flange 315 on bushing 306 and a gasket317. A plug 318 is threadably received within valve body 301 and bearsagainst a flexible gasket 319. Plug 318 supports stem 303 for axialmovement with respect thereto. Radially extending outlet openings 320are provided in stem 303 for discharging liquid fuel in atomized forminto the passage 166 leading to the combustion chamber.

The metered charge of liquid fuel within metering chamber 308 is placedin fluid communication with passage 305, when stem 303 is moved inwardlysince openings 320 are disposed to the left of gasket 319, and theliquified gaseous fuel expands into the combustion chamber throughpassages 305 and 166. When the stem 303 is shifted to the right, asviewed in FIG. 10, under the influence of spring 310, the inclinedportin of stem 303 moves away from O-ring 314 and a fresh charge ofliquid fuel passes into chamber 308 between stem portion 313 and O-ring314.

Metering valve body 301 is associated with liquified gas container 330by the insertion of inlet stem 302 within an outlet passage 331 at theupper end of container 330. The outlet passage 331 is associated with aconventional valve 332, forming no part of the present invention. Thecontainer 330 is preferably formed of metal to provide appropriatebursting strength, and supported within container 330 is a bag 333 ofgenerally cruciform shape which has a threaded upper end 334 threadablyassociated with valve 332. Bag 333 is collapsible, and containstherewithin a given volume of liquified gas. A suitable propellant 335,such as propane, is provided between the bag 333 and the inner wall ofcontainer 330 for applying pressure to bag 333 for expelling liquid fueloutwardly of valve 332, and into the metering valve through inletpassage 304.

In most preferred embodiments of the invention a suitable lubricatingmedium is associated with, and dispersed within the liquid fuel in bag333. The lubricating medium may take the form of a lubricating oil,which is mixed as a minor percent with the liquid gas in bag 333. It hasbeen found that such a lubricating medium not only does notsignificantly detract from ignition of the liquid fuel in the combustionchamber or from flame propagation therewithin, but also reduces wear onthe moving parts thus prolonging the useful life of the metering valveand other moving parts of the tool.

A portable gas-powered tool with this novel linear motor can be used fora variety purposes, depending on the attachments connected to the motor.For example, as illustrated in the embodiments of FIGS. 2-5 and 6-7, itcan be used to drive fasteners. Also, of course, attachments can beconnected to the working member of the linear motor for shearing treelimbs, connecting hog rings, animal tags, piercing holes, marking metalplates, etc. In substance, it can be used anywhere where a large forceis required. As stated, this tool is fully portable, can be light inweight, and thus can be used anywhere independent of the need for anexternal source of power, such as compressed air.

The novel motor is made possible in a relatively small portable tool bythe creation of turbulance in the combustion chamber prior to and duringcombustion. This has not been done before in a portable tool and whileit is acknowledged that internal combustion engines are notoriously old,these all require an external source of power in order to start theengine. The fan causes the air and fuel to be mixed to a generallyhomogeneous state under atmospheric conditions, and continued operationof the fan increases the burning speed of the fuel-air mixture in thecombustion chamber prior to and during movement of the working member.In this tool, no external source of power is required and starting ofthe tool is totally independent of movement of the working member. Thistool utilizes liquified gas, and thus is very economical to operate.Actually, it is about one half the cost of operating a pneumatic toolpowered by a gasoline driven air compressor. As stated above, arelatively small portable tool adaptable for many uses can be designedemploying the invention.

Thus, it will be appreciated from the foregoing description that thepresent invention provides an improved portable tool operated by alinear motor which has many advantages and improvements. While theinvention has been described in conjunction with several embodiments, itis intended that many alternatives, modifications, and variations willbe apparent to those skilled in the art. Accordingly, it is intended tocover by the appended claims all such alternatives, modifications, andvariations that are within the spirit and scope of the invention.

What is claimed is:
 1. A self-starting portable tool comprising ahousing, a cylinder in said housing, a piston in said cylinder andforming a motor member, a working member attached to said piston, acombustion chamber formed within said housing and having said pistondefining a wall portion thereof, a turbulence generator in said chamber,means for supplying fuel and air to said chamber, means for operatingsaid generator independent of said piston such that premixing andturbulence are imparted to the air and fuel in said chamber beforeinitial ignition of the mixture in said chamber and before initialmovement of said piston, and means for igniting and exploding saidmixture in said combustion chamber to .[.deive.]. .Iadd.drive.Iaddend.said piston to operate said working member, whereby the initialand all subsequent strokes of the motor member are operated at.[.substantiall.]. .Iadd.substantially .Iaddend.full energy output andfurther wherein the turbulence generator consists of a fan disposed insaid chamber and the means for operating said generator includes anelectric motor self-contained within said housing and connected to saidgenerator.
 2. A portable tool in accordance with claim 1 including meansfor returning the piston to its driving position after it has beendriven.
 3. A portable tool in accordance with claim 2 including meansfor admitting air under ambient pressure to the underside of the pistonwhen it is in its driven position such that the pressure differentialbetween the ambient pressure on the underside of the piston and thelower pressure on the other side of the piston is effective to returnthe piston to its driving position.
 4. A portable tool in accordancewith claim 2 including means for retaining the piston in its drivingposition after it has been returned thereto.
 5. A self-starting portabletool comprising a housing, a cylinder in said housing, a piston in saidcylinder and forming a motor member, a working member connected to saidpiston, a combustion chamber formed within said housing and having saidpiston defining a wall portion thereof, means providing axially disposedinlet and exhaust ports to said combustion chamber for admitting air andfor discharging the products of combustion, a turbulence generator insaid chamber axially disposed between said inlet and exhaust ports,means for supplying fuel to said chamber, means for operating saidgenerator independent of said piston such that premixing and turbulenceare imparted to the air and fuel in said chamber before initial ignitionof the fuel in said chamber and before initial movement of said piston,and means for igniting and exploding the mixture in said combustionchamber to drive said piston to operate said working member and furtherwherein the turbulence generator comprises a fan having its axis axiallydisposed in said chamber, which fan serves to scavenge said chamberafter firing by directing air from said inlet port through said exhaustport, and the means for operating said generator includes an electricmotor self-contained within said housing and connected to saidgenerator.
 6. Apparatus in accordance with claims 1 or 5 in which themeans for supplying fuel to said chamber is a metering valve mechanismwherein a prescribed amount of fuel is supplied to said combustionchamber.
 7. Apparatus in accordance with claims 1 or 5, wherein themeans for igniting said fuel includes a spark plug powered by apiezo-electric device.
 8. Apparatus in accordance with claims 1 or 5,including trigger operated means for operating the means for supplyingfuel to said chamber and for igniting said fuel to drive said motormember.
 9. A portable tool in accordance with claim 5 in which thecombustion chamber is opened and closed by a valve means that coactswith said inlet and exhaust ports, and means for effecting movement ofsaid valve means to close off said chamber prior to ignition and opensaid chamber after the working member has been driven to facilitatescavenging of said chamber.
 10. A portable tool in accordance with claim9 in which the valve means includes a slidable sleeve that cooperateswith the housing to effect opening and closing of the inlet and exhaustports.
 11. Apparatus in accordance with claims 9 or 10, includingtrigger operated means for (1) operating said valve means to control theopening and closing of said combustion chamber, (2) operating the meansfor supplying fuel to said chamber, and (3) for igniting said fuel todrive said motor member.
 12. A portable tool in accordance with claims 9or 10 including trigger operated means for operating said valve means tocontrol the opening and closing of said combustion chamber. .Iadd.
 13. Aself-starting portable tool comprisinga housing, an elongated cylinderin said housing, a piston having an upper face and a lower face, saidpiston being mounted in said cylinder to be driven between an upperposition of rest and a lowermost position and forming a motor member, aworking member attached to said piston, a combustion chamber formedwithin said housing and having the upper face of said piston defining awall portion of said combustion chamber, means for providing a fuel andair mixture in said chamber, means for igniting and exploding saidmixture in said combustion chamber to drive said piston through adriving stroke from said upper position to said lowermost position tooperate said working member, and return means for causing said piston tomove upwardly from said lowermost position to said upper position ofrest, said return means including outlet means in said elongatedcylinder between its ends for communicating said cylinder with ambientatmosphere and being disposed below said upper position of rest andabove said lowermost position of said piston, such that when said pistonis driven towards said lowermost position, said piston moves past saidoutlet means thereby to place said combustion chamber in communicationwith said outlet means to exhaust a portion of combustion gases fromsaid combustion chamber to ambient atmosphere and cause a reduction intemperature of the combustion gases remaining in the combustion chamber,and said return means further including bumper means at the lower end ofthe cylinder for initially moving said piston upwardly from saidlowermost position, said combustion chamber above said upper face beingout of communication with ambient atmosphere during the further returnof said piston to said upper position of rest, said further return ofsaid piston to said upper position of rest being substantially caused bythroughout further such return, said return means producing an upwardlyacting pressure differential on said upper and lower faces of saidpiston induced by the reduction in temperature of the combustion gasesabove the upper face to produce a sharp reduction of pressure in saidcombustion chamber to below ambient pressure. .Iaddend. .Iadd.14. Aself-starting portable tool in accordance with claim 13, and whereinsaid outlet means comprises a plurality of ports. .Iaddend. .Iadd.15. Aself-starting portable tool in accordance with claim 13, and whereinsaid outlet means is located in the lower end of the cylinder. .Iaddend..Iadd.16. A self-starting portable tool in accordance with claim 13, andwherein said outlet means is in communication with ambient atmospherewhen said piston is both thereabove and therebelow through an exhaustvalve which opens in response to an elevation in the pressure internallyof said cylinder at said outlet means above ambient pressure, whichcloses in response to a reduction to ambient pressure internally of thecylinder in the zone of said outlet means, and which remains closedunder the influence of the reduction of pressure during the furtherreturn of the piston to the upper position of rest. .Iaddend. .Iadd.17.A self-starting portable tool in accordance with claim 16, and whereinsaid exhaust valve is adapted to open in response to movement of saidpiston downwardly during the driving stroke towards said outlet means,as well as in response to exposure to the elevated pressure of thecombustion gases in said combustion chamber when said piston movesdownwardly past said outlet means. .Iaddend. .Iadd.18. A self-startingportable tool in accordance with claim 13, and wherein said bumper meanscomprises a superatmospheric air bumper in the lower end of saidcylinder which is generated after said piston moves downwardly past saidoutlet means, and one-way valve means in said cylinder below said outletmeans for opening and communicating with ambient atmosphere when thepressure in the cylinder below the piston drops below ambient pressure..Iaddend. .Iadd.19. A self-starting portable tool in accordance withclaim 16, and wherein when the piston moves downwardly past said outletmeans, there is rapid exhausting of the combustion gases therethroughand the exhaust valve is rapidly reclosed, rapid further temperaturereduction of remaining combustion gases in the combustion chambercausing a sharp reduction in the pressure of the combustion gases abovethe piston, the differential between that pressure and ambient pressurebelow the piston inducing said further return of the piston to its upperposition of rest. .Iaddend. .Iadd.20. A self-starting portable tool asset forth in claim 13, including exhaust valve means in communicationwith said outlet means for exhausting air beneath the piston as it movesthrough its driving stroke, the portion of the cylinder below saidexhaust valve means, the piston lower face and the housing adjacent thebottom of the cylinder providing a sealed compression chamber wherebythe air below the piston and exhaust valve means is compressed to forman air bumper to prevent the piston from contacting the housing adjacentthe bottom of the cylinder, said air bumper comprising said bumpermeans. .Iaddend.
 21. A self-starting portable tool as set forth in claim20, in which the portion of the housing adjacent the bottom of thecylinder includes at least one one-way check valve which opens tointroduce ambient air to assist in returning the piston to its upperposition of rest after it has been driven and the combustion gases havebeen exhausted and a pressure below ambient pressure exists above theupper face of the piston.